For some combinations of Ubuntu guest OS version and VMware vCenter version, newly provisioned Ubuntu VMs may not boot completely and be stuck at the Grub bootloader (observable through vCenter or CloudBolt console feature).
If upgrading vCenter or changing Ubuntu template version is not a viable solution (see the VMware guest OS customization support matrix for supported configurations), then the following may be tried as a workaround to get the server to finish booting regardless of any issues with customization:
/boot/grub/grub.cfg file on your Ubuntu template and look for a line that reads:
if [ "$recordfail}" = 1] ; then set timeout=-1
Change the timeout to something like:
This prevents Grub from waiting for user-input after a failed shutdown.